# import re
# import  time
# import requests
# import uuid
#
# #1.发送请求
# url_page = 'https://mm.enterdesk.com/dongmanmeinv/'
# ret = requests.get(url=url_page)
# # print(ret.text)
#
# url_lst = re.findall(r'https://up.enterdesk.com/edpic_360_360/.*?\.jpg',ret.text)
#
#
# for url in url_lst:
#     res = requests.get(url=url)
#     time.sleep(2)
#     #将响应数据转换为二进制流数据
#     content = res.content
#
#     #3.将二进制流数据转化为二进制流数据
#     name = str(uuid.uuid1()) +'.jpg'
#     with open(name,'wb') as f:
#         print('正在下载%s' % name)
#         f.write(content)

# [1,2,2,1,3]  找出不重复的
# import numpy
#
# a = numpy.array([1,2,2,1,3])
# b = numpy.unique(a)
# print(b)



# 小球 案例
# a = int(input("请输入高度"))
# count = 0
# while a/2>0.1:
#     a = a * 0.5
#     count += 1
#     print(f"第{count}次弹出{a}米")

# 等比数列
# 等比数列的第n项

# def func(h, n):
#     a1 = h/3
#     an = a1 *(1/3**(n-1))
#     sn = (a1- an * (1/3)/(1-1/3))
#     print(an, sn)
# func(3, 2)

# 时间复杂度
# import  time
# start = time.time()
# list = []
# for i in range(1, 1000001):
#     list.append(i)
# end = time.time()
# print(start-end)
#
# s1 = time.time()
# tet = [i for i in range(1, 11000001)]
# e1 = time.time()
# print(s1-e1)

def Fib(n):
    if n == 0 :
        return 0
    if n == 1:
        return 1
    if n == 2:
        return 2
    return Fib(n-1) + Fib(n-2)

n = int(input("请输入台阶"))
print(Fib(n))







# def bubble_sort(array):
#     for i in range(1, len(array)):
#         for j in range(0, len(array) - i):
#             if array[j] > array[j + 1]:
#                 array[j], array[j + 1] = array[j + 1], array[j]
#     return array
#
#
# if __name__ == '__main__':
#     array = [10, 17, 50, 7, 30, 24, 27, 45, 15, 5, 36, 21]
#     print(bubble_sort(array))


# import re
# import  time
# import requests
# import uuid
#
# #1.发送请求
# url_page = 'https://mm.enterdesk.com/dongmanmeinv/'
# ret = requests.get(url=url_page)
# # print(ret.text)
#
# url_lst = re.findall(r'https://up.enterdesk.com/edpic_360_360/.*?\.jpg',ret.text)
#
#
# for url in url_lst:
#     res = requests.get(url=url)
#     time.sleep(2)
#     #将响应数据转换为二进制流数据
#     content = res.content
#
#     #3.将二进制流数据转化为二进制流数据
#     name = str(uuid.uuid1()) +'.jpg'
#     with open(name,'wb') as f:
#         print('正在下载%s' % name)
#         f.write(content)


# def func(a):
#     c = []
#     for i in a:
#         if i not in c:
#             c.append(i)
#     return c
# a=[1,2,1,3,5,5]
# print(func(a))

# with open('test.txt','r',encoding='utf8') as file:
#     list1 = [tuple([int(j.strip()) for j in i.split(',')]) for i in file.readlines()]
# print(list1)


# def func(a):
#     li = []
#     parentheses = "()[]{}"
#     for i in range(len(a)):
#         si = a[i]
#         if parentheses.find(si) == -1:
#             continue
#         if si == '(' or si == "{" or si == '[':
#             li.append(si)
#             continue
#         if len(li) ==0:
#             return False
#
#         p = li.pop()
#         if(p=='(' and si == ')' or p=='{' and si == '}' or p=='[' and si == ']'):
#             continue
#         else:
#             return False
#     if len(li)==0:
#         return True
#     else:
#         return False
#
# a = '(){}'
# print(func(a))
